Revert "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)

Will reland in two different commits to preserve git blame history.

BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org

Change-Id: I550da8525aeb9c5b8f96338fcf1c9714f3dcdab1
Reviewed-on: https://chromium-review.googlesource.com/554610
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18820}

webrtc/rtc_base/asyncpacketsocket.cc

@@ -1,29 +0,0 @@
-/*
- *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#include "webrtc/base/asyncpacketsocket.h"
-
-namespace rtc {
-
-PacketTimeUpdateParams::PacketTimeUpdateParams()
-    : rtp_sendtime_extension_id(-1),
-      srtp_auth_tag_len(-1),
-      srtp_packet_index(-1) {
-}
-
-PacketTimeUpdateParams::~PacketTimeUpdateParams() = default;
-
-AsyncPacketSocket::AsyncPacketSocket() {
-}
-
-AsyncPacketSocket::~AsyncPacketSocket() {
-}
-
-};  // namespace rtc